1. Field of the Invention
The present invention relates generally to methods for momentarily heating the surface of a mold and system thereof, and particularly to a method for momentarily heating the surface of a mold and system thereof, which is capable of momentarily heating the surface of the mold prior to injection molding and cooling a molded product immediately after the molding, thereby improving the quality of products in appearance, preserving the physical and thermal properties of resin in the products, and increasing the productivity of a manufacturing process of the products for the reduction of the manufacturing cost of the products.
2. Description of the Prior Art
In a technical field where resin (such as synthetic resin, plastics or the like) products are manufactured, various attempts have been made to momentarily heat a mold to the same temperature as that of resin while the cavity of the mold is being filled with the resin, and to rapidly cool the mold after the cavity of the mold is filled with the resin. The object of these attempts is to increase the quality of products in appearance, to improve the strength and thermal properties of the products and to increase the productivity of the manufacturing process of the products for the reduction of the manufacturing costs of the products.
German Pat. Appln. No. 297 08 721.5 and PCT Appln. No. WO 98/51460 disclose a mold capable of being temporarily heated by the flame of gaseous fuel and synthetic resin forming method thereof. According to the above described patents, a synthetic resin injecting mold process is automated and the molded products of synthetic resin may is manufactured continuously.
However, according to the above-described patents, since a molded product cannot be cooled immediately after the forming of the product, the quality of the molded product is reduced in appearance, the strength and thermal properties of the injection-molded product are deteriorated and the productivity of the molding process is reduced.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method for momentarily heating the surface of a mold, which allows the mold to be filled with molten resin for injection molding after the preheating of the mold to a predetermined temperature and allows an injection-molded product to be cooled upon the completion of the injection molding, thereby increasing the quality of the injection-molded product in appearance and improving the strength and thermal properties of the injection-molded product.
Another object of the present invention is to provide a system for momentarily heating the surface of a mold, which comprises upper and lower molds for forming resin and performing the heating of the upper and lower molds, a supply unit for supplying air and gaseous fuel, a safety unit for preventing the danger of gas explosion, and a control unit for controlling the operation of the above components.
A further object of the present invention is to provide a method for momentarily heating the surface of a mold and system thereof, in which one or more cores are disposed between its upper and lower molds, the cores are momentarily heated using gaseous fuel or an induction heater, and heating and cooling are performed in the process of injection molding, thereby improving the quality of an injection-molded product.
In order to accomplish the above object, the present invention provides a method for momentarily heating a surface of a mold, comprising the steps of: opening upper and lower molds of the mold, and supplying gaseous fuel; injecting and igniting the gaseous fuel from the lower mold after allowing the upper and lower molds to come close to each other at a predetermined distance; heating the upper mold for a predetermined time period; filling a forming space between the upper and lower molds with molten material through the upper mold immediately after stopping heating and closing the upper and lower molds; cooling a molded product by injecting compressed air to the molded product after allowing the upper and lower molds to be opened at a predetermined distance; and ejecting the molded product from the upper and lower molds after allowing the upper and lower molds to be completely opened.
In addition, the present invention provides a system for momentarily heating the surface of a mold, comprising: a casting material feeder for supplying molten casting material; upper and lower molds for forming a predetermined shaped cast; an injection molding control for controlling the upper mold and the lower mold; an air and gaseous fuel mixture and supply unit for supplying compressed air and gaseous fuel simultaneously or selectively; a gaseous fuel mixture and supply control for controlling the operation of the air and gaseous fuel mixture and supply unit; an interface for interfacing the injection molding control and the gaseous fuel mixture and supply control; and a control panel for visually displaying the control, condition and operation of the components of the system.